1. Field of the Invention
This invention relates to a display device using cathode ray. This invention also relates to a method of driving the display device.
2. Description of the Prior Art
U.S. Pat. No. 4,451,846 discloses an advanced flat-type cathode-ray tube display which includes a plurality of parallel line cathodes for producing respective electron beams, a screen exposed to the electron beams and converting them into corresponding lights, and a plurality of parallel control grid electrodes for modulating the levels of beam current of the respective electron beams in accordance with display data. The flat type display also includes several groups of other grid electrodes, vertical scanning electrodes, and beam deflecting and focusing electrodes.
In the flat type display of U.S. Pat. No. 4,451,846, since the electron beams are respectively modulated by the separate control grid electrodes, even small errors in positional relationships of the control grid electrodes with the other electrodes or the cathodes can cause considerably unequal modulations of the electron beams and cause an unacceptable inequality in the electron beams. In addition, since each of the control grid electrodes is in the form of a plate, the capacitances between the control grid electrodes and adjacent electrodes are large. In other words, the load capacitance of a modulation circuit including the control grid electrodes is large.
U.S. Pat. No. 4,535,272 also discloses a flat-type cathode-ray tube display including a plurality of parallel line cathodes. In this display, the line cathodes are heated by currents which are supplied from a power source via respective switching transistors. Each of these switching transistors periodically moves between a conductive state and an unconductive state, so that the supply of the heating current to the associated line cathode is periodically enabled and inhibited. Specifically, during a period in which one line cathode is allowed to emit electrons, the supply of the heating current to the line cathode is interrupted. During other periods, the supply of the heating current to the line cathode is enabled. This periodical or intermittent supply of the heating currents to the line cathodes via the switching transistors is to save electric power.